Apparatus for dual temperature exchange



July 28, 1964 J. S. SPEVACK APPARATUS FOR DUAL TEMPERATURE EXCHANGE Original Filed Sept. 29, 1950 s Sheets-Sheet 1 INVENTOR.

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APPARATUS FOR DUAL TEMPERATURE EXCQANGE Original Filed Sept. 29, 1950 5 Sheets-Sheet 2 a I B v 5 5n 89 i n6.- Id INVENTOR.

J'eRoME. Spas/ink, BY 7Q A/y'vr'fl/ July 28, 1964 .1. s SPEVACK APPARATUS FOR DUAL TEMPERATURE EXCHANGE Original Filedsept. 29, 1950 3 Sheets-Sheet 3 Qw 5 w m l l l I l I Ilfllllll llllnlh ll ILIIIII II I I l IN INVENTOR. JEROME \SPQVACK' BY yea I United States Patent Oftice 3,142,540 Patented July 28, 1964 This application is a division of my copending parent application Serial No. 188,925, filed September 29, 1950,

HDS H 0 D S HDO ZHDS 2HDO :r.

now Patent No. 2,895,803, issued July 21', 1959, and relates to the apparatus aspects of the invention therein disclosed, which apparatus is particularly but not exclusively adapted for the concentration of isotopes by the method disclosed and claimed in said parent application which involves the concentration of a desired material by the dual temperature exchange system.

In such systems, for instance, as disclosed in my copending application Serial No. 509,581, filed November 9, 1943, now Patent No. 2,787,526, issued April 2, 1957, each stage of a cascade employs a cold tower and a hot tower and the progress of the exchange reactions through the system has required alternate and repeated cooling and heating of the substances involved in a very costly manner. These temperature reversals taken with the humidity variations have constituted the outstanding factors in the operating costs and have been determinative of the practicability of the system.

An object of this invention is to provide apparatus particularly but not exclusively adapted for use in an isotope exchange system of this type in which the temperature and humidity controls will be exercised in a simple efficient manner economizing on the energy to be supplied and greatly reducing the cost of operation while at the same time maintaining the rate and quality of output.

Further objects of the invention, particularly in integrating the successive stages to cooperate by interchange between them in both the hot and cold reactions and reduce dependence on extraneous supplies of heat and cold, will appear from the following specification taken in connection with the accompanying drawings in which:

FIGS. 1a, 1b, 1c, and 1d show diagrammatically an arrangement of apparatus according to the present invention;

FIGS. 2a and 2b show diagrammatically, a modification;

FIG. 3 is a diagram of a further modification.

The system is typically illustrated in connection with the concentration of deuterium by countercurrent reactions at contrasting high and low temperatures. The reactants in this exemplary embodiment are hydrogen sulfide gas (H S) and liquid water (H).

Both of these substances contain chemically different forms of hydrogen, which are capable of undergoing a reversible exchange reaction. In such a reaction an equilibrium is established between the light and heavy hydrogen isotopes. Since the mechanism of the exchange reaction is ionic, no catalyst is required.

13+ sn 0119 13+ 813-) 11+ sD) (11+ 013-) The apparatus at each stage makes use of two towers, a cold temperature tower and a hot temperature tower. The isotopic exchange reactions involved in this illustrative embodiment are:

HDS 1120 ms HDO ms 11150 HDS D20 HDS ms ms HDO :2 mo D20 Expressed in ionic form, the above chemical exchange equilibria are:

0 (H+ SH") (D+ sD) H s Dis O'D) i 20 D20 primary ions may further ionize as:

sn- ++s- OD- D++ o- Equilibrium conditions favor concentration of the denterium in the water phase with a greater concentration effect occurring at the lower temperature. Proper operation of the system gives rise to a concentration gradient in the towers and causes an accumulation, in this illustrative embodiment, of deuterium as heavy water at the bottom of the cold tower.

Feed water enters the system at the top of the cold tower, passes through the cold tower into the top of the hot tower, and leaves as waste from the bottom of the hot tower which waste may in turn be used as the supply to a separate subsequent system. Hydrogen sulfide gas is continuously recycled from the top of the cold tower to the bottom of the hot tower, always flowing countercurrent to the water. Suitable heat exchangers are provided to heat or cool the gas and liquid streams before their entry into the towers.

In each stage'the cold tower acts as the concentrating tower. Inasmuch as equilibrium conditions favor the presence of deuterium in the water phase, then as the water stream passes through the cold tower it becomes enriched in deuterium, while the hydrogen sulphide stream becomes depleted. Depletion of deuterium in the gas stream continues to a point where at the top of the cold tower it approaches its equilibrium concentration with the feed water.

The function of the hot tower is the reverse of the cold tower. This tower acts as a deuterium stripper, and thereby provides deuterium reflux to the cold tower.

HQS HDO HDS D20 Wherein the Since the equilibrium constant at the hot tower tempera ture is not as favorable to deuterium concentration in the water, the water which has passed into the hot tower from the cold tower is obliged to return its excess deuterium to the hydrogen sulphide stream. This redistribution of deuterium from liquid to gas goes on through the entire length of the hot tower and continues to a point where at the bottom of the hot tower the waer approaches its equilibrium concentration with the hydrogen sulphide. Therefore, since the quantity of deuterium entering with the hydrogen sulphide at the bottom of the hot tower is essentially the same as that which has left the top of the cold tower, and since the liquid and gas streams tend to approach equilibrium with each other at either end of the system, then the deuterium concentration in the water leaving the hot tower must be less than 3 its concentration in the feed water which enters the cold tower.

By repeated operation, this mechanism causes a growing accumulation of deuterium at the bottom of the cold tower and thereby enables the continuous removal of a concentrated product.

In the arrangement of FIGS. 1a1d the supply of liquid, e.g., water, enters at and passes through conditioner 11 and pump 12 to the top of the cold tower 14 of the first stage. As hereinafter explained, there is a countercurrent of gas (H 8) passing upward in this tower 14, the temperature of this cold exchange reactor being maintained at about 20 C., for instance, for a pressure of 5 atmospheres.

The cold liquid discharged at 15 at the bottom of the tower by pump 19 is divided, one portion going by conduit 16 through heat exchanger 17 to be heated thereby and passed on to the top of the hot tower 18 of this first stage. Here again there is a countercurrent of gas for the hot (80 C.) exchange reaction and the hot liquid discharged at 20 at the bottom of the tower is passed by pump 21 and conduit 22 through stripper 67 and heat exchanger 23 removing the gas (H S) from the liquor and raising the temperature of the liquor which then passes through conduit 24 to heat exchanger 17 where it serves to raise the temperature of the first stage liquid passing from the cold to the hot tower. The discharge of this circulation of heating liquid from exchanger 17 passes to waste.

The other portion of the cold liquid discharged from the cold tower at 15 passes by conduit 25 to the top of the cold tower 28 of the second stage for the cold (20 C.) reaction with the upward sweeping countercurrent of gas and the cold liquid discharged at 29 passes through pump 30 and in part through pipe 31 and heat exchanger 32 raising the temperature of the liquid for entry at 33 into the hot tower 36 where it meets the countercurrent of gas, this hot reaction being at about 80 C. and discharging the hot liquid at 37 to pump 38 passing the liquid through pipe 39 to the top of the hot tower 18 of the preceding stage.

The remainder of the cold discharge from tower 28 passes by piping 40 to the top of the cold tower 42 of the third stage where it is reacted by the countercurrent gas and discharged at 43 to be passed by pump 44 and by piping 45 to heat exchanger 46 raising its temperature for discharge through piping 47 to the top of the hot (80 C.) tower 48 and is subjected to reaction with the countercurrent gas and discharge at 49 through pump 50 passing the hot liquid through piping 51 to the top of the next preceding hot tower 36.

The other part of the cold discharge from tower 42 passes by pipe 52 to the top of the fourth stage cold tower 56 at 20 C. where it reacts with the countercurrent gas and is discharged at 53 through pump 54 and piping 55 to heat exchanger 57 and piping 58 to the hot tower 60. The discharge of hot liquid from this tower at 61 is passed by pump 62 and piping 63 to the top of the hot tower 48 of the preceding stage, completing the circuit of the liquid within the system unless additional stages are found advantageous.

No temperature treatment is required for the liquid flows to the cold towers assuming an initial supply at the right temperature and the liquids supplied to the hot towers are raised in temperature by the waste discharge from the primary hot tower 18, waste pipe 24 being connected to feed pipe 65 leading to the heat exchangers 32, 46 and 57 of the second, third and fourth stages respectively. The temperature regulation of the liquid is thus provided from sources within the system and additional steam is only drawn upon in connection with the final stripping of the discharge liquor at 67 and return of the separated gas to the hot tower 18.

This stripping arrangement is another feature of the improved system wherein the gas (H 8) is removed from the waste liquor in a simple but effective way at essentially no extra energy expense. It comprises means by which the amount of process steam that is still required by the plant to make up for process inefiiciencies and to complete the gas heating and humidification at the various stages as hereinafter explained, is put to an additional use before it enters the hot tower 18. This steam entering at 66 is passed countercurrent to the processed waste liquor in the contact stripping tower 67. In this manner the dissolved hydrogen sulphide is removed from the waste liquor and swept back through outlet pipe 68 to the hot tower 18 together with the steam. Stripping efiiciency which leaves less than one part per million residue may be attained. The hot liquid discharge at 69 from stripper 67 is circulated in heat exchanger 23 to increase the temperature of the waste liquor supply to the subsequent heaters 17, 32, 46 and 57 for the liquid entering the hot towers, the liquor being raised, for instance, from C. in conduit 22 to C. in conduit 24.

The conditioning of the countercurrent gas (for instance H S) is attained by the new apparatus with utmost economy. The gas supplies to the cold towers are efficiently cooled and dehumidified and the gas supply to the first stage hot tower is heated and humidified with interchange of energy between these operations while the hot towers of the remaining stages receive their supplies from the hot towers of the previous stages, so that all treatment of the gas supplies to the second, third and fourth stage hot towers is dispensed with.

This results in a type of cascade system which integrates the plant so that each stage is not an independent unit but is a working part of the overall system. The hot humidified gases required at the bottom of the second stage hot tower 36 are obtained through piping 70 from the hot gases leaving the hot tower 18 of the first stage, and all of the hot liquor from the hot tower 36 of the second stage returns by piping 39 to the hot tower 18 of the first stage. Similarly hot tower 48 receives its gas supply from preceding hot tower 36 by piping 71 and returns to tower 36 its hot liquor discharge by piping 51, while hot tower 60 receives its hot gas through pipe 72 from the preceding hot tower 48 and returns to tower 48 its hot liquid discharge through pipe 63.

The final discharge of hot gases from fourth stage hot tower 60 pass out through piping 74 to subsequent conditioning treatment and is then used to supply the countercurrent gas to cold tower 56 of the fourth stage.

An important aspect of the present system is the recovery and use of the low level energy which is available in the cooling and dehumidification of the hot gases leaving the hot towers to condition these gases for countercurrent use in the cold towers. Instead of cooling these hot gases with cooling water and wasting the heated water, the latter is circulated in a cyclic treatment reclaiming the heat and using it for heating and humidification in the arrangement illustrated.

The hot gases from the tower 18 must be cooled and dehumidified before they can be used in the cold tower 14 of this first stage and the same problem is presented at each following stage. A supply of these hot gases from tower 18 on their way to the cold tower 14 are passed through the dehumidifier and gas cooler 75 which is cooled by water supplied by pipe 76. This water raised in temperature is fed by pipe 77 to the top of a special humidifier tower 78 and through this tower 78 the cold gases brought by pipe 79 from first stage cold tower 14 are passed in direct contact countercurrent to the hot water. By this efiicient direct contact method the cold gases are simultaneously heated and humidified while the circulating liquor is cooled. The hot humidified gases are passed by pipe 80 into the hot tower 18. The cooled liquor is recirculated to the dehumidifier and cooler 75 to pick up another charge of energy for delivery to the humidifier 78. Inasmuch as the liquid circulates in a closed cycle 75, 77, 78, 76, there is no effect upon the deuterium concentration in the gas stream which enters the hot tower. A small amount of make-up water is continuously added to this liquor cycle in order to replace that portion which is consumed in humidification of the gas stream. This may conveniently be drawn from the discharge pipe 22 from hot tower 18 or from the feed, etc.

A further advantage of the system is that all of the energy from the dehumidifiers of all of the stages is available for humidification and gas heating in the humidifier 78 of the first stage. These stages, two, three and four, receive their hot gases direct from the preceding stage in each case and so humidifiers for these stages are dispensed with. In each of these stages the corresponding dehumidifier and cooler 84, 85, 86 intervening in the gas passage between the hot tower and the cold tower is cooled by circulation from pipe 82, drawing its supply from pipe 76, and pipe 83 returning the discharges to pipe 77 so that these dehumidifiers 84, 85, 86 of these subsequent stages are in circuit with the cyclic circulation through humidifier 78 and supply energy thereto.

The cooled gases from hot tower 18 pass into the bottom of cold tower 14 at 87 and are joined there by the cold gases brought from the cold tower 28 by pipe 88, gas pump 89 and pipe 90. Similarly the cold tower 28 is supplied at 91 with cooled gases from hot tower 36 and at 92 with cold gases from tower 42, while tower 42 receives cooled gases at 93 from hot tower 48 and at 94 is supplied with cold gases from cold tower 56, which latter tower receives its supply of gases at 95 solely from hot tower 60.

In addition to the dehumidifying and cooling of the hot gases at 75, 84, 85, 86 they may be subjected to a separating action by appropriate means associated with each stage, arranged as is separator 97 of the first stage, which is connected for receiving the discharge from cooler 75 and separating out the liquid which is passed by pump 88 to heater 99 and delivered into the top of the hot tower 18. The energy for heater 99 is supplied from an outside source. The gas discharge from separator 97 is further cooled in aftercooler 188 supplied with cooling circulation from any suitable source and the condensate from this aftercooler is carried into tower 14 with the gas stream. Similar condensers and coolers may be provided at the subsequent stages as shown.

In the final stage the separator 181 separates out the liquid content of the gases from condenser 86 and pump 102 delivers the condensate to discharge pipe 103 and heater 104 from which the liquid raised in temperature is returned to the hot tower 60.

The condensate drawn oil? in discharge pipe 103 as the product of this primary plant is high in concentration of HDO and D 0 and may serve as a supply for further concentration in additional stages or another system if desired.

The overall process practiced by this illustrative embodiment of the invention relies on ordinary water as the deuterium source; the gas, hydrogen sulphide, merely acts as an exchange medium and is recycled without being consumed. Make-up gas in small amounts may be supplied preferably at the entrance to the cold tower of the first stage.

The diagrammatic showing and descriptions herein are merely illustrative and descriptive of the plant and its operation in the illustrative application, and changes in tower height, number of stages, temperature or operation, pressure of operation, the kinds of substances used, the particular material to be concentrated, the use of catalysts to enhance rate of exchange, variations of design within a countercun'ent temperature exchange and other details may be resorted to within the principle of the invention.

The modification diagrammed in FIGS. 2a and 2b is shown with four stages the first of which has the hot reaction divided between three parallel hot towers 118. In general the handling of the flows and the connections of the reactors and stages are similar and the parts in FIGS.

2a and 2b are in most instances numbered one hundred above the numbers applied to the corresponding parts in FIGS. 1a to 1d. For simplicity the pumps have been omitted from FIGS. 2a and 2b and the liquid stream is in full lines and the gas stream in broken lines. The heat exchange between the towers of FIGS. 2a and 2b is modified and does not employ the closed circuit fluid circulation typified by 75, 76, 77, 78 of the system of FIGS. la to 1d. Instead, a supply of the hot gases from towers 118 on their way to the cold tower 114 are passed by conduit 288 to heat exchanger 178 and are cooled and have their moisture in part condensed by the countercurrent of a flow of the cold gases from tower 114 by pipe 179. The partially cooled gas from exchanger 178 is passed by pipe 281 to the secondary cooler and condenser 282 and thence by pipe 203 to the cold tower 114. The cooling circulation indicated at 209 for cooler-condenser 2112 is supplied from an outside source.

In this system of FIGS. 2a and 2b the heat exchanger 178 raises the temperature of the cool gases received from cold tower 114 and at the same time provides heat for vaporization of the moisture for humidification, the makeup water for humidification being fed in at 205 at the entrance to the heat exchanger. Condensate from exchangers 178 and 202 are collected and delivered through pipes 206, 207 respectively wholly or in part to the top of the cold tower of the next succeeding stage.

In a similar manner a supply of the hot gases from towers 136, 148 and on their way to the cold towers 128, 142 and 156 respectively are passed to heat exchangers 184, and 186 respectively and are cooled and have their moisture in part condensed by the countercurrent of a supply of cold gases from tower 114 by pipes 219, 221 and 223 respectively. The said supplies of gases from tower 114 are raised in temperature in heat exchangers 184, 185 and 186 and at the same time heat is provided for vaporization of moisture for humidification, this make-up water for humidification being fed in at 228, 222 and 224 respectively.

In any system of heat recovery between fluids entering and leaving either the hot or cold chemical exchange towers, there may be direct physical contact only between the fluids entering and leaving, respectively, a single end of the tower. This limitation is necessary to avoid a redistribution of concentrated material from an enriched fluid to a depleted fluid. Accordingly, the system described herein has made use of the very efiicient direct intimate contact methods of heat transfer together with the indirect non-contacting methods as required for this process. For example, in FIGS. 1a to 1d the energy available from the gas leaving the hot tower is transferred by indirect contact heat exchanger (75, FIG. 1a; 84, 85,

86, FIG. 1c) to water which in turn transfers the energy by direct contact (intimate mixing in a countercurrent tower 78, FIG. 1b) with the gas entering the bottom of the hot tower. In this way it is possible to simultaneously heat and humidity the gas entering the hot tower. Likewise in FIGS. 2a and 2b, in exchanges 178, 184, 185 and 186 there is a simultaneous heating of the gas and vaporizing of the water required for humidification.

Another modified system may be employed in which the heat exchanges between the hot and cold flows are in general the reverse of those employed in FIGS. 1a and 1b. This modification makes use of a heat transfer cycle involving the pick-up of energy from a hot humidified gas by a liquid stream in a counter-current direct contact, gas cooler dehumidifier tower and the subsequent liberation of this energy from the liquid to a cold gas stream by indirect contact in a countercurrent heat exchanger.

In this modification (FIG. 3) the cold tower 314'may be extended to include a section 314a at its bottom (or a separate tower) which will serve as the direct contact gas cooler-dehumidifier. The cold liquid from the bottom of the cold tower 314 together with an auxiliary flow via 31411 passes countercurrent in 314a in contact with the hot humidified gas from the top of the hot tower 318 and becomes heated as the gas is cooled to the cold tower temperature. The cooled gas via 387 then flows upward through the cold tower 314. The hot liquid from the bottom of said direct contacting section 314:: is divided. A portion 3140 represented by the main cold tower stream plus the added condensate is sent to the hot tower and the balance 314d is sent to a heat exchanger 391 through which indirectly it transfers its energy to a mixture of the cold tower gas and a volume of liquid required for humidification, and thus the cold tower gas outflow 314 is simultaneously heated and humidified as the liquid in 314d is cooled. To make up for inefficiencies of the heat transfer equipment this liquid is further cooled in 314g, as required, before returning it to the same direct contacting section 314a via 314b.

With the systems of this invention the operating conditions for the illustrative embodiments described are readily attained Within moderate ranges of the typical values set forth in the following tabulations:

Cold Tower Temperature 35 Hot Tower Temperature 70 80 190 Operating Pressure (absolute) appro. .p.s.1- 80 275 Gas to liquid ratio in cold tower (mols HzS/ mols H20) 2. 21 2. 20 1. 8 Concentration of deuterium in product from final stage percent 2 2 2 Number of stages 4 4 4 Ratio of liquid flow of a s cceed g stage to a preceding stage 1/4 1/4 1/4 Concentration of deuterium in feed water pereent 0143 0143 0143 Recovery of deuterium from feed water do 12 12 21 The enrichment at which the product may be removed from the system is not dependent on the operating temperatures alone. It is determined by the overall contacting etficiency of the countercurrent towers which in turn is dependent upon the efficiency of the individual bubble plates or contacting members Within the towers. For bubble plate towers of the standard design generally obtained, approximately 80 plates per tower would be required for conditions set forth above.

The molar ratios of total gas to total liquid passing countercurrent in each stage of hot and cold towers are determined so that the corresponding operating lines intervene between the equilibrium curves as represented by the effective fractionation factors for each of the said towers. The effective fractionation factor in the illustrative embodiment is the equilibrium ratio of the mol or atom fraction of total deuterium in the gas phase to the mol or atom fraction of total deuterium in the liquid phase at a particular temperature and pressure.

In the design of a multiple stage cascade system the relative cross-sectional area of each stage is governed by fluid flows in that stage. The number of theoretical plates in any stage is determined by the fluid flow rates, the extraction efiiciency of that stage, the desired enrichment for that stage and the net enriched fluid removal from that stage. In the application employed for illustration, the concentrations existing at the ends of the towers of each stage are calculated by the mathematical solution of deuterium, water and hydrogen sulphide material balances with allowance for the net deuterium transport to each successive stage of an amount equal to the steady state deuterium extraction from the feed water.

The relative size of flows in each stage are based on economic considerations and such factors as hold up and equilibrium time.

In deuterium concentration effected by use of this system there is also a concentration of the tritium and at a better fractionation factor, the principal equilibria being indicated as follows:

This invention thus provides a practical and highly efficient system for producing a substance (herein exemplified by water) containing a first material (herein exemplified by (D) deuterium) concentrated therein, by exchanging, at two different temperatures, said first material (exemplified by D) with a second material (exemplified by H) between chemically different fluid substances (exemplified by hydrogen sulfide and water) which are physically separable from each other, and which are each capable of containing each of said materials (D and H).

I claim:

1. Apparatus for producing a fluid containing a first material concentrated therein by exchanging, at two different temperatures, said first material with a second material between chemically diflerent fluids which are physically separable from each other and which are each capable of containing each of said materials, which apparatus comprises (a) a series of at least two pairs of exchange units each of which has first fluid and second fluid ingress and egress means for counter-current flow of the two fluids therethrough; (b) means in each of said units for mixing said two fluids therein to cause an exchange of the said materials between the two fluids; (c) means for maintaining a first unit of each pair at a temperature to cause the first fluid flowing therethrough to become enriched and the second fluid flowing therethrough to become impoverished with respect to said first material; (d) means for maintaining the second unit of each pair at a temperature to cause the second fluid flowing therethrough to become enriched and the first fluid flowing therethrough to become impoverished with respect to said first material; (e) means connected to the first fluid egress means of the first unit of each pair and to the first fluid ingress means of the second unit of said pair for transferring a first part of the enriched first fluid from the first unit of each pair to the second unit of said pair; (f) means connected to the first fluid egress means of the first unit of each pair except the last pair of the series and to the first fluid ingress means of the first unit of the next succeeding pair for transferring a second part of the enriched first fluid from the first unit of each pair except the last of said pairs to the first unit of the next succeeding pair; (g) means connected to the second fluid egress means of the second unit of each pair and to the second fluid ingress means of the first unit of said pair for transferring a first part of the enriched second fluid from the second unit of each pair to the first unit of said pair; (h) means connected to the second fluid egress means of the second unit of each pair except the last pair of the series and to the second fluid ingress means of the second unit of the next succeeding pair for transferring a second part of said enriched second fluid from the second unit of each pair except the last to the second unit of the next succeeding pair of units; (i) means connected to the first fluid egress means of the second unit of each pair except the first pair of the series and to the first fluid ingress means of the second unit of the next preceding pair for transferring impoverished first fluid from the second unit of each pair of units except the first pair to the second unit of the next preceding pair of units; (j) means connected to the second fluid egress means of the first unit of each pair except the first pair of the series and to the second fluid ingress means of the first unit of the next preceding pair for transferring impoverished second fluid from the first unit of each pair of units except the first pair to the first unit of the next preceding pair of units; and (k) means connected to an enriched fluid egress means of the last pair of units for removing enriched fluid from the last pair of exchange units of said series.

2. Apparatus according to claim 1, further comprising means connected to the first fluid egress means of the second unit of said first pair of units for stripping from the impoverished first fluid leaving the second unit of the first pair of units a content of said second fluid carried thereby, said stripping means being separate from said second unit of said first pair and having ingress means for first fluid in liquid phase, means for supplying first fluid in gaseous phase, egress means for stripped first fluid and egress means for second fluid stripped therefrom, and means connected to the egress means for second fluid of said stripping means and to the second unit of said first pair of units for passing the uncondensed portions of said first fluid in gaseous phase with the stripped content of said second fluid to the second unit of said first pair of units, said apparatus also comprising regenerative heat exchange means connected to the first fluid egress means of said second unit of said first pair, to the first fluid ingress means of said stripping means, and to the egress means for first fluid in liquid phase of said stripping means for passing the stripped first fluid and the condensate from the first fluid introduced in gaseous phase, as they leave the stripping means, in heat exchange relation with the first fluid in liquid phase being passed to the stripping means from the second unit of said first pair of units as aforesaid, whereby the temperature in the stripping stage is substantially higher, and the temperature of the stripped first fluid after said heat exchange is also higher, than the temperature of the first fluid leaving the second unit of said first pair of units.

3. Apparatus according to claim 1 further comprising direct contact heat exchange means and indirect contact heat exchange means and means connected thereto for circulating a cyclic flow of first fluid therebetween, said direct contact heat exchange means being connected to the second fluid egress means of a second unit of a pair of units and to the second fluid ingress means of the first unit of said pair of units, and said indirect contact heat exchange means being connected to a fluid egress means of a first unit and to a fluid ingress means of a second unit of a pair of units, thus providing for the bringing of an enriched second fluid being transferred from a second unit to a first unit of a pair of units into direct contact heat exchange relation to a cyclic flow of first fluid, and for then bringing said cyclic flow into heat exchange rela tion to a fluid passing from a first unit to a second unit of one of said pairs of units.

4. Apparatus according to claim 3, in which the first fluid is liquid, the second fluid is a gas, and the temperature maintained in the second unit of each pair of units is higher than the temperature maintained in the first unit of said pair, and in which the fluid egress and ingress means to which said indirect contact heat exchange means is connected are the second fluid egress means of the first unit of said pair and the second fluid ingress means of the second unit of said pair, said apparatus further comprising means connected to said indirect heat exchange means for introducing a quantity of first fluid into the second fluid being heated therein by said cyclic flow of first fluid.

5. Apparatus according to claim 1, further comprising direct contact heat exchange means and indirect contact heat exchange means and means connected thereto for circulating a cyclic flow of first fluid therebetween, said direct contact heat exchange means being connected to the second fluid ingress means of the second unit of said first pair of units and to the second fluid egress means of the first unit of said first pair of units, and said indirect contact heat exchange means being connected to the second fluid egress means of the second units of a plurality of pairs of units and to the second fluid ingress means of the first units of a plurality of pairs of units of said first pair of units, thus providing for at least in part cooling the enriched second fluid streams being transferred from second units to first units of a plurality of pairs of units by indirect heat transfer to a body of first fluid, as well as for at least in part heating and saturating the second fluid stream entering the second unit of said first pair of units by direct contact thereof with the so heated body of first fluid.

6. Apparatus according to claim 5, further comprising means connected to the first fluid egress means of the second unit of said first pair of units and to the said direct contact heat exchange means for transferring to said heated body impoverished first fluid from the second unit of said first pair of units.

7. Apparatus according to claim 3 in which said direct contact heat exchange means is also connected to the first fluid egress means of a first unit of a pair of units and to the first fluid ingress means of the second unit of said pair of units.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,142 ,540 July 28 1964 Jerome 8.. Spevack It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 10, line 20, for "of said" read of which one is said Signed and sealed this 8th day of April 1969.

(SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer 

1. APPARATUS FOR PRODUCING A FLUID CONTAINING A FIRST MATERIAL CONCENTRATED THEREIN BY EXCHANGING, AT TWO DIFFERENT TEMPERATURES, SAID FIRST MATERIAL WITH A SECOND MATERIAL BETWEEN CHEMICALLY DIFFERENT FLUIDS WHICH ARE PHYSICALLY SEPARABLE FROM EACH OTHER AND WHICH ARE EACH CAPABLE OF CONTAINING EACH OF SAID MATERIALS, WHICH APPARATUS COMPRISES (A) A SERIES OF AT LEAST TWO PAIRS OF EXCHANGE UNITS EACH OF WHICH HAS FIRST FLUID AND SECOND FLUID INGRESS AND EGRESS MEANS FOR COUNTER-CURRENT FLOW OF THE TWO FLUIDS THERETHROUGH; (B) MEANS IN EACH OF SAID UNITS FOR MIXING SAID TWO FLUIDS THEREIN TO CAUSE AN EXCHANGE OF THE SAID MATERIALS BETWEEN THE TWO FLUIDS; (C) MEANS FOR MAINTAINING A FIRST UNIT OF EACH PAIR AT A TEMPERATURE TO CAUSE THE FIRST FLUID FLOWING THERETHROUGH TO BECOME ENRICHED AND THE SECOND FLUID FLOWING THERETHROUGH TO BECOME IMPROVERISHED WITH RESPECT TO SAID FIRST MATERIAL; (D) MEANS FOR MAINTAINING THE SECOND UNIT OF EACH PAIR AT A TEMPERATURE TO CAUSE THE SECOND FLUID FLOWING THERETHROUGH TO BECOME ENRICHED AND THE FIRST FLUID FLOWING THERETHROUGH TO BECOME IMPROVERISHED WITH RESPECT TO SAID FIRST MATERIAL; (E) MEANS CONNECTED TO THE FIRST FLUID EGRESS MEANS OF THE FIRST UNIT OF EACH PAIR AND TO THE FIRST FLUID INGRESS MEANS OF THE SECOND UNIT OF SAID PAIR FOR TRANSFERRING A FIRST PART OF THE ENRICHED FIRST FLUID FROM THE FIRST UNIT OF EACH PAIR TO THE SECOND UNIT OF SAID PAIR; (F) MEANS CONNECTED TO THE FIRST FLUID EGRESS MEANS OF THE FIRST UNIT OF EACH PAIR EXCEPT THE LAST PAIR OF THE SERIES AND TO THE FIRST FLUID INGRESS MEANS OF THE FIRST UNIT OF THE NEXT SUCCEEDING PAIR FOR TRANSFERRING A SECOND PART OF THE ENRICHED FIRST FLUID FROM THE FIRST UNIT OF EACH PAIR EXCEPT THE LAST OF SAID PAIRS TO THE FIRST UNIT OF THE NEXT SUCCEEDING PAIR; (G) MEANS CONNECTED TO THE SECOND FLUID EGRESS MEANS OF THE SECOND UNIT OF EACH PAIR AND TO THE SECOND FLUID INGRESS MEANS OF THE FIRST UNIT OF SAID PAIR FOR TRANSFERRING A FIRST PART OF THE ENRICHED SECOND FLUID FROM THE SECOND UNIT OF EACH PAIR TO THE FIRST UNIT OF SAID PAIR; (H) MEANS CONNECTED TO THE SECOND FLUID EGRESS MEANS OF THE SECOND UNIT OF EACH PAIR EXCEPT THE LAST PAIR OF THE SERIES AND TO THE SECOND FLUID INGRESS MEANS OF THE SECOND UNIT OF THE NEXT SUCCEEDING PAIR FOR TRANSFERRING A SECOND PART OF SAID ENRICHED SECOND FLUID FROM THE SECOND UNIT OF EACH PAIR EXCEPT THE LAST TO THE SECOND UNIT OF THE NEXT SUCCEEDING PAIR OF UNITS; (I) MEANS CONNECTED TO THE FIRST FLUID EGRESS MEANS OF THE SECOND UNIT OF EACH PAIR EXCEPT THE FIRST PAIR OF THE SERIES AND TO THE FIRST FLUID INGRESS MEANS OF THE SECOND UNIT OF THE NEXT PRECEDING PAIR FOR TRANSFERRING IMPROVERISHED FIRST FLUID FROM THE SECOND UNIT OF EACH PAIR OF UNITS EXCEPT THE FIRST PAIR TO THE SECOND UNIT OF THE NEXT PRECEDING PAIR OF UNITS; (J) MEANS CONNECTED TO THE SECOND FLUID EGRESS MEANS OF THE FIRST UNIT OF EACH PAIR EXCEPT THE FIRST PAIR OF THE SERIES AND TO THE SECOND FLUID INGRESS MEANS OF THE FIRST UNIT OF THE NEXT PRECEDING PAIR FOR TRANSFERRING IMPROVERISHED SECOND FLUID FROM THE FIRST UNIT OF EACH PAIR OF UNITS EXCEPT THE FIRST PAIR TO THE FIRST UNIT OF THE NEXT PRECEDING PAIR OF UNITS; AND (K) MEANS CONNECTED TO AN ENRICHED FLUID EGRESS MEANS OF THE LAST PAIR OF UNITS FOR REMOVING ENRICHED FLUID FROM THE LAST PAIR OF EXCHANGE UNITS OF SAID SERIES. 